I actually know a young woman who recently completed her thesis on this very topic; bring back the joy of play to ever increasingly stressed out adults in urban settings. Get them outside and moving in non threatening ways and give them the opportunity to play, like kids, again. This is awesome
New York Introduces Its First Adult Playground – NYTimes.com.
Fitnessgroan's Blog 
I find it interesting that exercise is supposed to be unpleasant. We even go as far as to make a motto out of “no pain; no gain”. My wife says she cannot stand exercise but loves to go to a dance class — that just happens to leave her exhausted.